This term defines, in general, a device which is inserted in a lumen, for example, a vascular duct and, in particular, an arterial duct, usually by means of an endolumenal-prosthesis transport system, or stent delivery system (SDS), and is then expanded or spread out in situ in order to support the walls of the lumen locally. The main object of this support is to eliminate the blockage, for example, brought about by a stenosis, and to prevent the re-formation thereof.
A general treatise on endolumenal prostheses or stents can be found in the works “Techniques in coronary artery stenting” by Colombo and Tobis, Martin Dumitz Ltd., 2000 and “Handbook of cardiovascular interventions” by Ulrich Sigwart, Michel Bertrand, Patrick W. Serruys, Harcourt Brace & Company Limited, 1996.
Endovascular prostheses are generally known. However, the term “endovascular prosthesis” has been used interchangeably with other terms such as “stent” or “expandable prosthesis”. The term “vascular prosthesis” used in this description should be understood as including any expandable prosthetic device for implantation in a human or animal duct (such as, for example, a lumen, an artery, a vessel, a respiratory duct, a gastrointestinal duct, a bile duct, or the like).
A large number of patent documents relating to endolumenal prostheses have been filed in the past, for example: U.S. Pat. No. 4,733,665 (Palmatz), U.S. Pat. No. 4,739,762 (Palmatz), U.S. Pat. No. 4,800,882 (Gianturco), U.S. Pat. No. 4,907,336 (Gianturco), U.S. Pat. No. 5,035,706 (Gianturco et al.), U.S. Pat. No. 5,037,392 (Hillstead), U.S. Pat. No. 5,041,126 (Gianturco), U.S. Pat. No. 5,102,417 (Palmatz), U.S. Pat. No. 5,147,385 (Beck et al.), U.S. Pat. No. 5,282,824 (Gianturco), U.S. Pat. No. 5,316,023 (Palmatz et al.), CA 1,239,755 (Wallsten), CA 1,245,527 (Gianturco et al.), CA 2,134,997 (Penn et al.), CA 2,171,047 (Penn et al.), CA 2,175,722 (Penn et al.), CA 2,185,740 (Penn et al.), CA 2,192,520 (Penn et al.), PCT/CA97/00151 (Penn et al.), PCT/CA97/00152 (Penn et al.), PCT/CA97/00294 (Penn et al.), EP 0 895 760 (Bartorelli), EP 0 888 093 (Penn et al.), EP 1 151 730 (Hojeibane), EP 0 956 832 (Richter et al.), PCT/US98/08194 (Dubrull).
An endolumenal prosthesis has to fulfil two somewhat conflicting requirements.
First of all, the endolumenal prosthesis has to have a high degree of flexibility when it is in its non-expanded state to facilitate the delivery of the prosthesis through the tortuous anatomy as far as the implantation site. Moreover, when the prosthesis is in the expanded condition, it has to demonstrate sufficient radial stiffness to minimize the collapse of the walls of the duct in which it has been deposited and, for example, re-stenosis effects, as well as effectively resisting the possibility of acute occlusion. These conflicting requirements, that is, the provision of a prosthesis which has considerable flexibility when in the non-expanded condition whilst having great radial stiffness in the expanded condition, have been achieved in the past with the use of struts that are interconnected, typically with a longitudinal arrangement, to confer great flexibility on the prosthesis in the non-expanded or contracted condition, and further interconnected struts, for example, nonlongitudinal circumferential lines or rings of struts, which open up to rings that are stiff radially (at least in an ideal situation), to confer the necessary radial stiffness on the prosthesis in expanded conditions.
A solution which partially satisfied these requirements was proposed in US patent application 2002/0065547 (Moore).
There is nevertheless still a further great need to find an endolumenal prosthesis which can easily be clenched in a radially contracted position around delivery and expansion devices (SDS). This need in fact conflicts particularly with the need to have interconnected circumferential struts that are capable of withstanding radial stresses adequately when in the expanded condition. In fact these struts are difficult to clench around the delivery and expansion devices (SDS) precisely because of their structural capacities.